Various proposals have conventionally been made of polyphenol compounds containing trisphenol and methods of producing the same. For example, Japanese Unexamined Patent Publication No. Sho. 57-34122 proposes polyphenol compounds obtained by condensation reaction of hydroxybenzaldehydes with phenols.
Further, Japanese Unexamined Patent Publication No. Sho. 63-182326 proposes a method of condensation reaction of unsaturated aldehydes such as crotonaldehyde, with phenols in the presence of sulfonic acid catalyst.
However, epoxy resin cured products using those polyphenol compounds as, for example, curing agents for epoxy resins are superior in heat resistance, but are liable to absorb water. For that reason, those polyphenol compounds involve the problems such as occurrence of package cracks when used as materials for encapsulation for semiconductors and decrease in insulating properties when used as an electrically insulating material.
On the other hand, Japanese Unexamined Patent Publication No. Hei. 4-26642 proposes the use of novolak compound for the purpose of improving water resistance, which comprises a bisphenol having an alicyclic structure in the molecule available from limonene or the like.
However, the epoxy resin cured products using this polyphenol compounds as curing agents for epoxy resin are superior in water resistance, but involve the problems that heat resistance and flame retardancy decrease, thereby being not preferable in view of a high temperature reliability.
As described above, the conventional polyphenol compounds involve the problem of water resistance or heat resistance when used as curing agents for epoxy resin.